Digital printer hammer assembly

ABSTRACT

A hammer assembly for use in on-the-fly type digital printers. A central block portion has top and bottom hammer retaining plates extending outwardly in overhanging fashion from said block to receive hammer aligning pins in aligned apertures in the plates. Each of the hammer aligning pins has connected to it a spring beam member with a loop which elongates as the hammer is thrust upwardly from the block assembly when actuated, said loop recoiling as the spring biases the hammer pin assembly back to its resting position.

United States Patent 1191 1111 3,745,917 Cavella 1 July 17, 1973 [54] DIGITAL PRINTER HAMMER ASSEMBLY 3,386,377 6/1968 Dalton 101/93 C 3,468,246 9/1969 L e et a1 1 101/93 C [75] James h Phlladelpma, 3,556,002 1 1971 Bfagg 101 93 c 73 Assi nee: Datad ne oration Kin of 3,631,797 1/1972 Johnston et al... 101/93 l g Prussii Pa p g 3,636,860 1/1972 Johnston et al 101/93 Filed: June 1971 Primary Examiner-William B. Penn 2 App] 153, 35 Att0rney-Woodcock,Washburnet a1.

[52] 0.8. CI 101/93 C 7] ABSTRACT [51] Int. Cl B41] 9/10, B41] 1/48 A hammer assembly for use in on the fly type digital [58] Field of Search 101/93 C, 109, 297, Printers A central block portion has top and bottom 101/287 hammer retaining plates extending outwardly in overhanging fashion from said block to receive hammer References cued aligning pins in aligned apertures in the plates. Each of UNITED STATES PATENTS the hammer aligning pins has connected to it a spring 3,072,045 1/1963 Goin 101/93 c beam member with 8100p which eJOngateS as the 3,087,421 4/1963 Irwin et al 101/93 C mer is thrust upwardly from the block assembly when 3,090,297 5/1963 Wilkins et a1... 101/93 C actuated, said loop recoiling as the spring biases the 3,187,668 6/1965 Marsh 101/93 C hammer pin assembly back to its resting position 3,301,177 1/1967 Shepard 101/93 C 3,359,921 12/1967 Arnold et al 101/93 C 14 Claims, 4 Drawing; Figures so 42 k PAIENIEB 4m 1 1 ms SHEIZUFZ DIGITAL PRINTER HAMMER ASSEMBLY BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to print hammer assemblies and in particular a print hammer assembly which is used in digital printer of the on-the-fly type. The hammers function to strike against a moving print drum on which raised characters are engraved or mounted thus causing a print out on interposed tape. The hammers are aligned in close fashion and in position to strike when actuated the closely positioned characters to which they are aligned. A density of characters per linear inch is required by most printers. The hammers are actuated by solenoid actuators or other means, not a part of the present invention as described herein.

2. Prior Art A number of spring biased hammer assemblies are known in the prior art. One such type of assembly is shown in U. S. Pat. No. 3,309,989 issued Mar. 21, 1967 to K. Solheim et al. A drum-type printer is disclosed with a hammer that is spring connected to a hammer frame so that the hammer is biased to its return position after impact occurs. Another arrangement is disclosed in U.S. Pat. No. 3,209,682 issued Oct. 5, 1965 to A. C. Cooper, Jr. et al. Each hammer comprises a body portion, a striking arm and a firing arm and each hammer is pivotally mounted on a stationary support rod. A return spring is attached to a stationary support and has a free end which is in biasing contact with the body portion. Still aothr arrangement can be seen in U. S. Pat. No. 3,041,964 issued July 3, 1962 issued to V. R. Simpson et al. Although the disclosure is directed to a chaintype printer rather than a drum printer, the disclosure would also have utility with the latter. Hammers are aligned in a row and once actuated will bias back by leaf springs to their resting position.

In the above-cited disclosures and in other similar disclosures, several inherent problems are present. The hammers must be positioned in very close proximity to one another, i.e. if ten characters per linear inch are de sired, the need for a delicate design free of bulky complexities is self-evident. Regardless of whether the hammers and the actuators are combined or are separate as is the within contemplation of the present invention, size is a critical factor. Further, the hammers must be effectively returned to their rest position after they have been actuated. This is obviously critical where the hammers are separate from the actuator assembly. Also, when the hammers are separate from the actuator assembly, it becomes necessary to insure that they do not twist in their positions. In view of the close tolerances that must be observed in such a mechanism cost is an important consideration.

SUMMARY OF THE INVENTION It is, therefore, an object of the invention to provide a print hammer assembly which can be manufactured at relatively low cost.

It is another object of the present invention to provide a print hammer assembly in which the print hammers are effectively biased to their resting position by means of springs.

It is yet another object of the present invention to provide a print hammer assembly which utilizes a spring return but eliminates the spring interference which exists when coil springs are used.

It is still another object of the present invention to provide a print hammer assembly in which the print hammers are prevented from twisting in their bearing positions.

It is a further object of the present invention to provide a print hammer assembly in which hammers and springs may be mass manufactured and are interchangeable and easily replaced.

It is a still further object of the present invention to provide a print hammer assembly which meets the above objects and is sufficiently small in size to have utility in a line printer having 10 characters per linear inch.

In accordance with the objects 'of the invention a print hammer assembly is provided wherein a block member is used to space two hammer retaining plates. The hammer retaining plates have apertures which are aligned to receive the print hammer aligning plates. The apertures are spaced so that the hammers will be adjacent to each other, as is required to match the print characters on the print drum. Spring beams extend through the hammers without hollow pin members pressed into the print hammers. The spring beams each have a loop which elongates as the print hammers are thrust upwardly from the print block assembly. The spring beams are secured to the top of the hammer block assembly by a spring retaining clamp-type member. The extension of the spring beams through the hammers and for a considerable distance on the other side prevents the hammers from twisting in their bearing positions, yet allows the hammers to be thrust upwardly from the block assembly to impact against the print characters of the print drum. All hammers and springs are identically fabricated and are interchangeable.

Other features and advantages of the present invention will be apparent from the preferred embodiment hereinafter set forth and illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS sembly; and

FIG. 4 is an exploded view showing in detail the hammer pin assembly and the spring beam.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, an on-the-fly-drum type line printer is shown having a hammer block assembly I0 positioned adjacent a drum ]2 having print characters 13 (FIG. 2). An inked ribbon I4 extending through ribbon assembly 15 and paper 16 feeding from roll 17 along table assembly shown generally by 19 are guided between the hammer block assembly 10 and the print drum 12. Multiple hammer actuator means, the position of which is designated by 18, are placed in contacting relationship to the hammer pins 20 of the hammer block assembly 10. While the hammer block assembly 10 as hereinafter described has utility in the general type of line printer just described the operation of which will be described later, its utility extends to other type of line printers also.

Referring to FIGS. 2 and 3, the hammer block assembly 10 comprises a frame 21 having a central hammer block 22 having attached thereto a top hammer guide plate 24 and a bottom hammer guide plate 26. Rows of apertures 28 and 30 are drilled in the top and bottom hammer guide plates 24 and 26 respectively. The apertures 28 and 30 are aligned in rows so that hammer pin assemblies 20 may be received. Each hammer pin assembly comprises .a lower cylindrical pin portion 32 (see FIG. 3 and 4) and an upper rectangular portqon 34. The bottom 36 of the cylindrical portion receives the force of the actuator means which may be a solenoid device or other suitable means. The bottom of the rectangular portion as designated by 38 seen in FIGS. 3 and 4 abuts against the top hammer guide plate 24 to position the hammer pins 20 in their resting or nonprinting, position. The top 40 of the rectangular portion 34 is the impact area which strikes the paper 16 and ribbon 14 against the print characters 13 of drum 12. Thus by squaring the top of the hammer pin 20 to the extent shown the desired impact area configuration is achieved along with a configuration that is suitable to seat the hammer pin 20 in its resting position.

Pressed into the rectangular portion 34 of the hammer pin assembly is a spiral pin 42 which is a hollow member in which the hammer return spring in the form of a spring beam, 44 is inserted. As shown in FIGS. 2-4, the hollow pin 42 provides a bore which is substantially perpendicular to the longitudinal axis of the hammer pin 20 thus causing the spring beam 44 to be transverse to the hammer pin. The spring beam 44 made of music wire has a looped portion 46 and bent portions 48 and 49. The end of the spring designated by 50 is placed into the spiral pin 42 of the hammer pin assembly 20 and extends through it.

Referring to FIG. 4, a hammer spring retaining plate 52 and a block plate 53 are secured to the back of the hammer block 22 by screws 54 or other suitable means. The top lip portion 56 of the hammer spring retaining plate 52 bears against the top of the block plate 53. The outer bent portions 49 of the spring beams 44 are inserted in apertures 57in block plate 53 that are aligned with the hammer positions and are held firmly in place by the upper lip 56 of the hammer spring retaining plate 52. As can be seen in FIG. 4 the portion of the spring beam 44 designated as 48 is bent far in excess of 90 with respect to the adjoining portion of loop 46. Thus when the spring beam 44 is inserted in place and portion 48 is forced into approximately a 90 relationship with the adjoining portion of loop 46 the stress created aids in biasing the hammer pin 20 to its seated position after actuation.

Of critical importance is the aligning of hammer guide plates 24 and 26 so that corresponding apertures 28 and 30 are in exact alignment to receive hammer pins 20. Dowels 58 which extend through block 22 and into openings 60 in the guide plates 24 and 26, are used to achieve alignment and to serve as construction aids. Screws 62 are used to secure the guide plates 24 and 26 to the block 22.

In operation, print out occurs as the individual hammer pin assemblies 20 are actuated as selected characters are carried in turn past the pring hammers, the timed operation being performed in the conventional manner of line printers. The actuator means which comprises a number of individual actuators aligned with the hammer pin assemblies are actuated and impact against the bottom 36 of the hammer pin assembly.

Each individual hammer pin assembly is thus thrust upwardly or along its longitudinal olis from the hammer block 22 when actuated causing the spring 44 to elongate as permitted by loop portion 46. Once the hammer impact area 40 strikes against the drum characters 13, the spring bias of hammer return spring 44 will aid the hammer pin assembly 20 in reseating itself to its nonprinting portion with the lower portion of the square part 34 abutting the hammer guide plate 24.

As can be seen the elongation function of the spring beam loop 46 permits the hammer pin 20 to reach its destination as it is lifted by the actuation. The bias of the spring beam 44 aids in rapidly reseating the hammer pin 20 as the operation demands. The extension of the spring beam 44 through spiral pin 42 ensures that the hammer pin 20 will not twist on its axis and interfere with adjacent hammer pins. Thus it is unnecessary to use coil springs which are used extensively as return springs in other systems. Thus, interference problems with adjoining springs which result from the size of such springs when placed closely adjacent one another, are eliminated. I

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is: 1. An actuable hammer assembly for use in line printers comprising:

a frame member; hammer pins to be received by said frame member, said frame member having means by which said hammer pins may be aligned, slidably received, and supported, said hammer pins being movable along their longitudinal axes to a printing member from a nonprinting position upon actuation; and

a spring beam corresponding to each of said hammer pins, said hammer pins having guide means to slidably receive one end of each of said spring beams, each of said spring beams being secured at its other end remote from said associated hammer pin to assist in the return of the associated hammer pin after actuation to the non-printing position and further to prevent said hammer pins from twisting relative to each other.

2. The hammer assembly of claim 1 wherein said guide means opening comprises a hollow pin pressed into said print hammer pin which extends for a distance on the side opposite said hammer pin from where said spring beam enters provide an extension for said spring beam to further prevent said hammer pin from twisting.

3. The hammer assembly of claim 1 wherein each spring beam has a loop portion so that said spring beams may be elongated as said hammer pins move when actuated.

4. The hammer assembly of claim 1 wherein said spring beams are music wire.

5. A hammer assembly for use in on-the-fly line printers comprising:

hammer block structure having two retaining plates,

each of which has a row of longitdinally spaced apertures aligned with the other row;

hammer pins, including means for engaging at least one of said retaining plates to be thereby supported, said hammer pins being slidably inserted adjacent one another in said rows of aligned apertures so that each said hammer pin is receivable in an aperture in each row in such manner that when actuated, said hammer pins are thrust upwardly relative to said hammer block along their longitudinal axes and are then supported by said retaining plates upon their return to their nonprinting position after actuation as said means for engaging engages said at least one of said retaining plates; spring beam for each of said hammer pins positioned transverse to said respective hammer pin, one end of each said beam engaging said respective hammer pin, each of said beams having a loop which elongates as said hammer pins are actuated and thrust upwardly, said loop recoiling as each of said spring beams bias said hammer pins to their nonprinting position from said frame member; and means to secure to said frame member the end of each of said spring beams which is remote from said hammer pins.

6. The hammer assembly of claim 5 wherein said rows of apertures are spaced so that said hammer pins are engaged near opposite ends of said pins to ensure desired vertical alignment.

7. The hammer assembly of claim 6 wherein said means for engaging said at least one of said retaining plates is integral within said hammer pins.

8. The hammer assembly of claim 7 wherein said means for engaging at least one of said retaining plates comprises an enlarged portion of said hammer pins which is larger than the size of said apertures of one of said rows.

9. The hammer assembly of claim 5 wherein the securing means comprises holes in said hammer block structure for placement thereinto of the remote ends from said hammer pins of said spring beams and a clamp-like restraining plate secured to said hammer block structure which holds said spring beams in their holes.

10. The hammer assembly of claim 8 wherein part of said enlarged portion of said hammer pin is the hammer pin impact area which strikes against a moving print drum.

11. An actuable hammer assembly for use in on-thefly printers comprising:

a frame having a top guide plate and a bottom guide platewith a row of longitudinal spaced apertures in each said guide plate, said apertures of each row being aligned with an associated aperture in the other row;

hammer pins slidably inserted adjacent one another in said apertures in such manner that when actuated said hammer pins are thrust longitudinally along their axes, each of said hammer pins having means by which said hammer pins are supported within said apertures in their nonprinting position; and

spring beams associated with each said hammer pin serving to assist the return of said hammer pins after actuation to their nonprinting positions, each of said spring beams engaging a hammer pin at one end and being secured at its other end remote from said hammer pin.

12. The hammer assembly of claim 11 wherein each of said hammer pins has a bore extending through said hammer pin substantially perpendicular to the length of said hammer pin so that each of said spring beams may be inserted in said bore.

13. The hammer assembly of claim 12 wherein each of said hammer pins has a hollow pin pressed into it to provide said bore. 7

14. The hammer assembly of claim 13 wherein said spring beams are positioned above the top of said frame, and the supporting means is an enlarged portion of each of said hammer pins which abuts the top row of said frame apertures, said hollow pin being pressed into the enlarged portion of each of said hammer pins and extending for a' distance past each of said hammer pins from said frame so that said spring beams engage said hammer pins above the top of :said frame to ensure proper alignment of said hammer pins.

W CER'IIFLTCA'IE 01 COK'IULCTION Patent No. r 3,745,917 Dated Julv 17, 1973 Q linvcntofls) James J- Cavella ii: is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column l, line 31 delete "aothr" and insert "another' line 52, after "their" insert "bearing".

Column 2, line ZZ Hdelete' withont" and insert "within" Column 3 line 10, delete 'Portqon" and insert "nor-tier!" Column 4, line" 4 delete "olis" and insert "axis";

Colnmn 6, line 7, delete' longitndina'l and insert "longitudinally" Signed and sealed this 1st day of January 197k..

(sew Attest: r l r v i EDWARD M.FLETCHER,J R; RENE TEGTl EYER Attesting Officer Acting Commissioner of Patents 

1. An actuable hammer assembly for use in line printers comprising: a frame member; hammer pins to be received by said frame member, said frame member having means by which said hammer pins may be aligned, slidably received, and supported, said hammer pins being movable along their longitudinal axes to a printing member from a nonprinting position upon actuation; and a spring beam corresponding to each of said hammer pins, said hammer pins having guide means to slidably receive one end of each of said spring beams, each of said spring beams being secured at its other end remote from said associated hammer pin to assist in the return of the associated hammer pin after actuation to the non-printing position and further to prevent said hammer pins from twisting relative to each other.
 2. The hammer assembly of claim 1 wherein said guide means opening comprises a hollow pin pressed into said print hammer pin which extends for a distance on the side opposite said hammer pin from where said spring beam enters provide an extension for said spring beam to further prevent said hammer pin from twisting.
 3. The hammer assembly of claim 1 wherein each spring beam has a loop portion so that said spring beams may be elongated as said hammer pins move when actuated.
 4. The hammer assembly of claim 1 wherein said spring beams are music wire.
 5. A hammer assembly for use in on-the-fly line printers comprising: hammer block structure having two retaining plates, each of which has a row of longitdinally spaced apertures aligned with the other row; hammer pins, including means for engaging at least one of said retaining plates to be thereby supported, said hammer pins being slidably inserted adjacent one another in said rows of aligned apertures so that each said hammer pin is receivable in an aperture in each row in such manner that when actuated, said hammer pins are thrust upwardly relative to said hammer block along their longitudinal axes and are then supported by said retaining plates upon their return to their nonprinting position after actuation as said means for engaging engages said at least one of said retaining plates; a spring beam for each of said hammer pins positioned transverse to said respective hammer pin, one end of each said beam engaging said respective hammer pin, each of said beams having a loop which elongates as said hammer pins are actuated and thrust upwardly, said loop recoiling as each of said spring beams bias said hammer pins to their nonprinting position from said frame member; and means to secure to said frame member the end of each of said spring beams which is remote from said hammer pins.
 6. The hammer assembly of claim 5 wherein said rows of apertures are spaced so that said hammer pins are engaged near opposite ends of said pins to ensure desired vertical alignment.
 7. The hammer assembly of claim 6 wherein said means for engaging said at least one of said retaining plates is integral within said hammer pins.
 8. The hammer assembly of claim 7 wherein said means for engaging at least one of said retaining plates comprises an enlarged portion of said hammer pins which is larger than the size of said apertures of one oF said rows.
 9. The hammer assembly of claim 5 wherein the securing means comprises holes in said hammer block structure for placement thereinto of the remote ends from said hammer pins of said spring beams and a clamp-like restraining plate secured to said hammer block structure which holds said spring beams in their holes.
 10. The hammer assembly of claim 8 wherein part of said enlarged portion of said hammer pin is the hammer pin impact area which strikes against a moving print drum.
 11. An actuable hammer assembly for use in on-the-fly printers comprising: a frame having a top guide plate and a bottom guide plate with a row of longitudinal spaced apertures in each said guide plate, said apertures of each row being aligned with an associated aperture in the other row; hammer pins slidably inserted adjacent one another in said apertures in such manner that when actuated said hammer pins are thrust longitudinally along their axes, each of said hammer pins having means by which said hammer pins are supported within said apertures in their nonprinting position; and spring beams associated with each said hammer pin serving to assist the return of said hammer pins after actuation to their nonprinting positions, each of said spring beams engaging a hammer pin at one end and being secured at its other end remote from said hammer pin.
 12. The hammer assembly of claim 11 wherein each of said hammer pins has a bore extending through said hammer pin substantially perpendicular to the length of said hammer pin so that each of said spring beams may be inserted in said bore.
 13. The hammer assembly of claim 12 wherein each of said hammer pins has a hollow pin pressed into it to provide said bore.
 14. The hammer assembly of claim 13 wherein said spring beams are positioned above the top of said frame, and the supporting means is an enlarged portion of each of said hammer pins which abuts the top row of said frame apertures, said hollow pin being pressed into the enlarged portion of each of said hammer pins and extending for a distance past each of said hammer pins from said frame so that said spring beams engage said hammer pins above the top of said frame to ensure proper alignment of said hammer pins. 